Regulated radio frequency power supply



Oct. 25, 1949.- w. PARKER 2,485,652

REGULATED RADIO FREQUENCY POWER SUPPLY Filed Nov. lO,' 1947 i '1 :2 I) 110/10 26 73;! I I if? 1- :T i L "34 20 I I i 29 1 i REGULAR-0 our/=0;

3 Q e0 l6 I Q N'- g 37 INVENTOI Q. 12 .j I AOU/SMPAR/(ER J00 400 .500 am750 M/C/PO HMPEFES ATTORNEY Patented Oct. 2&3. 1949 I REGULATED RADIOFREQUENCY POWER SUPPLY Louis W. Parker, Little Neck, N. Y., asslgnor toInternational Standard Electric Corporation, New York, N. Y., acorporation of Delaware Application November 10, 194'], Serial No.784,999

6 Claims. (Cl. 321-18) This invention relates to regulated powersupplies, particularly for obtaining voltage regulation .of a lowcurrent at very high voltages.

A power supply for deriving direct current at high voltage is useful,among other things, for the operation of projection type televisionkinescopes. Regulation is particularly important if the focusingelectrode of a kinescope is supplied by another power supply. In thiscase it is imperative that the degree of regulation be similar for thetwo power supplies. Failing this condition defocusing takes place withconsequent changes in the average brilliancy of the reproduced picture.

Of course there are other uses to which a high voltage regulated powersupply may be put. Accordingly, it is a principal object of my inventionto provide a system for automatic voltage. regulation which may beapplied in a combination of two power supplies, one of which may be, for

example, a conventional rectified plate voltage supply, while the othermay be of the type which first generates a high voltage radio frequencyand then transforms the output to a still higher voltage, from which adirect current is obtained by rectification.

Another object of my invention is to provide a regulated power supply inwhich the degree of regulation of one of its components is maintainedsubstantially the same as in another component.

Still another object is to provide a regulated power supply system inwhich the control voltage applied to the grid of a certain voltageregulator tube is derived from the output of a radio frequency powersupply unit of the same system.

An important feature of the invention, as I have evolved it, is that thecathode of a certain voltage regulator tube is varied with respect toground potential by means of a voltage divider which is a component ofthe plate supply unit.

Another feature of the invention resides in the use of a control voltagefor a regulator tube which is derived from an output component of aradio frequency power supply.

My invention will now be described in more detail, reference being madeto the accompanying drawings in which:

Fig. 1 shows illustratively a preferred circuit arrangement of a powersupply system having improved features such as mentioned above, and

Fig. 2 shows a graph of regulated and unregulated voltages which figureis referred to in pointing out the advantages of my system.

Fig. 1 shows two main components of the power supply system. Thesecomponents are separately 55 former is enclosed in broken linerectangles. The first component to be considered is the plate supply Iwhich comprises the usual transformer 2 and rectifier tube 3. The outputis filtered conventionally by a series inductance l and a shuntcapacitor 5. This output is delivered first to the plates and screengrids of two amplifier tubes 6 which are connected in parallel. Secondlythe output is fed through a resistor l to the anode of a regulator tube8 which may be of triode type if desired. The anode of tube 8 isdirectly connected to the control grids in the tubes 6. The cathodes oftubes 6 are connected through resistors 9 to the screen grids in twoparallel-connected oscillator tubes l0. These screen grids are alsocoupled to ground through capacitors l I.

The cathode in the regulator tube 8 is connected to ground through aresistor l2 and is also connected to the cathodes of tubes 6 through anadjustable resistor It. The control grid in the regulator tube 8 derivesits control potential from a voltage divider which will be described inconnection with the radio frequency power supply unit.

A radio frequency output is obtained from the tubes III, which tubesconstitute principal components of a radio frequency power supply,indicated generally within the broken line rectangle It. The radiofrequency generated results from the use of inductances and capacitancestogether with a feed-backcircuit, as is more or less conventional. Inmore particular respects, the plate current for tubes i0'is fed from thecathodes in tubes 6 through a transformer winding [5 and thence toresistors it which are connected to the anodes in tubes H). The anodecircuit is made resonant by combining with the inductance IS anadjustable capacitor I! which is connected between the anode circuit andground. The cathode circuit for tubes In is also given a suitable timeconstant by virtue of a ground connection inclusiing resistor l8 inparallel with a capaci- The control grids in tubes [0 derive theirfeedback potential from a transformer winding 20 which is grounded atone end and is coupled to said control grids through a capacitor 2| inseries with grid resistors 22. The terminal of -capacitor 2| on theother side from the transformer winding 20 is also connected to groundthrough a resistor 23.

The transformer windings above mentioned are wound for mutual inductivereactance with other windings 24, 25 and 26. The complete transgiven thereference number 21. The

windings and 26 provide separate sources for the filaments in tworectifier tubes 28 and 23. The winding 24 may be considered the mainsecondary the output from which is to be rectified in the tubes 28 and29. At one terminal of the winding 24 is a connection to the anode oftube 20 and to the filament of tube 29. The other terminal of winding 24is coupled through capac itors 30 both to the filament of tube 28 andthe anode of tube II.

It will be apparent to those skilled in the art that the circuitcomponents for the radio frequency power supply it as above describedare suitably coordinated for the generation and rectification of a lowcurrent of very high voltage. The method of first producing oscillationsand then rectifying them is recognized as having many advantages for ahigh voltage power supply. One of the principal advantages is that powergeneration can be accomplished with very simple and low cost components.It is true that the rectifier tubes 20 and 29 must be of special designin order to prevent arcing and brush discharge between the electrodes.Such problems as these, however, have been met in the prior art.

The rectified output from the power supply unit It may be delivered toany suitable load, generally indicated by the rectangle I I. In shuntwith this load, however, I introduce as a featural component of myinvention a voltage divider of very high resistance comprising .aresistor 32 in series with a potentiometer 43. The tap it on thepotentiometer is directly connected to the control grid in the voltageregulator tube 8. Adjustment of the tap it permits the variousconditions of voltage regulation to be met, as will be pointed outpresently.

Because of the connection of the cathode in tube 8 to a junction pointbetween two resistors I2 and I3 and because of the fact that theseresistors are subject to a variable voltage drop dependent upon theoutput of current from the tubes 6, it will be observed that thiscathode is not maintained at a definite potential above ground. Theadvantage of this arrangement will also be explained in describing theoperation of the system.

The connection of the tap 34 to the potentiometer section 33 of thevoltage divider is one which is adjustable in a low voltage range aboveground. The voltage at the tap 34 may, therefore, be adjustedsatisfactorily for application to the grid of tube 8.

The regulation process of this system may be described as follows:

With a possible decrease in the resistance of the load ll there is aslight drop of voltage across the load and also across the dividerelements and It. This results in a slightly lower regulating voltage forapplication to the grid of the regulator tube 8. The plate current ofthis tube under this condition is decreased and the potential differencebetween the plate and ground of this tube rises, producing a lessnegative potential on the grids of tubes 8. This reduces the potentialdrop across the space paths of the tubes 8 and consequently increasesthe output potential of the entire plate supply unit I.

Now the oscillator tubes I. will give an increased output, due to thehigher D. C. potential which is supplied to their anodes and to theirscreen grids. The increased radio frequency output after rectificationin the tubes 28 and 29 will tend to bring back the voltage across theload 3| to the value which it held before the decrease of itsresistance.

The voltage regulation as supplied to the grid of tube 8 would not,however, produce ideal results. To improve the regulation further thecathode potential of the regulator tube 0 is preferably altered in theproper direction. This is done simply by obtaining the potential forthis cathode from the plate supply unit through resistors i2 and I3.

From the foregoing description of operation it may be seen that theoutput voltage of the plate 4 supply unit I is not held constant, butrather is increased with increasing load current on the radio frequencysupply unit It. The complete operation of the system, therefore. musttake into account this rise of potential between the cathode of thetriode tube 0 and ground when the load current is increased through theload 8|. These effects add up to far better regulation for the load I I.

By adjusting the resistance II it is possible to change the degree ofregulation until it becomes negative. Beyond this point instabilitywould result. Hence, it is important for satisfactory operation that theadjustment of resistor It be kept within workable bounds. However, ithas been found experimentally that the effective internal resistancewhich faces the load II can be made slightly negative without producingoscillations. It can also be varied between a slightly negative valueand several megohms without reducing efiiciency.

Referring now to Fig. 2, I show therein a curve 35 which has beenplotted from observations of a regulated power supply built inaccordance with the system herein disclosed. In comparison with thiscurve It I also show a curve of unregulated output 36 which was alsoobtained by the use of a radio frequency power supply lacking theregulating means which are supplied'for producing the curve 35. Curve 31has been plotted to show variations of input voltage as supplied to theanodes of tubes Ill. The coordinates of the chart represent kilovoltsalong a vertical scale and microamperes along a horizontal scale. Itwill be observed that the voltage regulation between the values of nocurrent and 700 microamperes is as nearly perfect as one could desire,whereas with unregulated power output there is an extreme drop involtage with an increase in current. The eflective internal resistancewithout the regulator operating was found in one instance to be 15megohms. By introducing the regulator this dropped to 0.2 megohm. Whenthe resistor II was suitably adjusted the effective internal resistancecould be still further reduced.

It was also observed in the performance of my improved system that acertain degree of adjustment of the resistor It was found desirable tocompensate for the ageing of the tubes and other slight variables ofoperating conditions.

While I have described and illustrated my invention as it might beapplied to a specific embodiment of a regulated power supply, it will beunderstood by those skilled in the art that various changes may be madeand other embodiments may be adopted which would also be comprehendedwithin the scope of the invention.

I claim:

1. In a high voltage power supply system of the type which includes aradio frequency generator, and means for rectifying the outputtherefrom, an electronic D. C. power supply unit having an anodalconnection to a source of positive D. C. potential and a floatingcathodal connection to the positive electrodes of said generator,regulator means for varying the cathode potential of said 5 unit, and acontrol circuit including a potentiometer connected across the outputterminals of said rectifying means and an adjustable tap on saidpotentiometer connected to a control electrode in said regulator means.

2. In' combination with a radio frequency generator and rectifier forsupplying a very high voltage current to a load, an electronic D. C.power supply unit for feeding a suitable potential to the pofltiveelectrodes of said generator, a regulator discharge tube having at leasta cathode, an anode and a control grid, a voltage divider connectedbetween the cathodal output terminal of said power supply unit andground, the cathode of said regulator tube being connected to anintermediate point on said divider, a, control electrode in said powersupply unit having a resistive connection to its more positiveelectrodes and a direct connection to the anode of said regulator tube,a potentiometer of relatively high resistance con-v nected in shunt withsaid load and having an adjustable tap thereon connected to the controlgrid of said regulator tube.

3. The combination according to claim 2 and including transformer meansfor feeding output energy from said generator to said rectifier.

4. The combination according to claim 2 and including transformer meansand connections therefrom to said rectifier whereby the output potentialof said generator is at least doubled.

5. In a high voltage power supply system, of the type which includes aradio frequency generator and means for rectifying the output from saidgenerator, an electronic circuit for supplying a variable platepotential to said generator, transformer means for raising the outputvoltage from said generator, means for rectifying said output voltage, avoltage regulator discharge tube suitably connected to said circuitarrangement which supplies plate potential and constituting means forcontrolling the voltage of said plate potential, and a potentiometerconnected across the output circuit of said output rectifying means,said potentiometer having an adjustable tap connected to a control gridin said voltage regulator tube, whereby said tube is caused to deliver aregulatory control voltage to said plate potential supply circuit.

6. The device according to claim 5 and including a voltage dividerconnected in shunt with said radio frequency generator, an intermediatepoint along this divider being connected to the cathode of saidregulator tube.

LOUIS W. PARKER.

No references cited.

